why chords with notes of different duration is not supported?

[Marc Mouries]

lilyponders,

i'd like to know about the rationale behind not supporting chords with notes of 
different duration.
In the case typesetting violin music it would be much simpler if the notation 
for chord allowed for notes of different duration.
It also applies to other instruments where chords are arpegiated and the top 
notes continue.

thanks,

-Marc